The long term objective of this research is to elucidate the mechanisms controlling the onset of adult ovarian activity at puberty in female mammals. The animal model to be employed in these studies is the immature ferret, in which precocious puberty can be induced by altering the photoperiod from a non-stimulatory, short day (8L: 16D) to a stimulatory long day 16L: 8D) at 15 weeks of age. The initial approach to this system will be a series of studies of light-induced puberty in the ferret which will determine the proximate endocrine events precipitating final ovarian maturation. These experiments involve determination of a) ovarian competence to respond to exogenous gonadotropin long before puberty, b) ovariectomy, with and without ovarian steroid replacement to distinguish between a steroid-independent, pubertal impetus to gonadotropin secretion, and a pubertal decrease in negative feedback efficacy of ovarian steroids on tonic gonadotropin secretion. After determining the primary endocrine basis of long-day induced puberty, it will be established whether spontaneous puberty in this species occurs via the same mechanism as photoperiod-induced puberty. Finally, this animal model of induced, precocious puberty will be employed to determine neural events which precede, and thus perhaps, induce, the final endocrine events of puberty. In this regard, changes in metabolic activity of specific areas of the hypothalamus which occur as a result of the pubertal stimulus will be examined via the uptake of 14C-2-deoxyglucose. In addition, timing of the activation of the arcuate nucleus-median eminence relative to the application of the light stimulus will be determined by hypothalamic deafferentation performed at specific intervals during induction of puberty.